Re: Some comments on the ansi test suite

>>>>> "Peter" == Peter Van Eynde <[email protected]> writes:

    Peter> Replace them with a better test would be nice. As most of them are fp
    Peter> problems we should (IMHO) replace them with "zero knowledge" tests or
    Peter> remove them.

How about the following tests:

;; sin(8*pi/2) = sin(4*pi) = 0.  Assume that our pi is a bit off.  Say
;; pi*(1+eps).  Then sin(8*pi*(1+eps)/2) = sin(4*pi + 4*pi*eps) =
;; sin(4*pi*eps) ~= 4*pi*eps.  Test for this, but allow a fudge factor
;; of 2.
(check-for-bug :alltest-legacy-1045
  (let ((y (sin (* 8 (/ pi 2))))
	(fudge 2))
    (< (abs y) (* fudge (* 4 pi long-float-epsilon))))
  t)

;; As in 1045, cos(pi*(1+eps)/2) = cos(pi/2+pi*eps/2) = -sin(pi*eps/2)
;; ~= -pi*eps/2.  Check that we are close enough.
(check-for-bug :alltest-legacy-1061
  (let ((y (cos (/ pi 2)))
	(fudge 2))
    (< (abs y) (* fudge (* pi long-float-epsilon 1/2))))
  t)

;; As in 1045, tan(x) = sin(x)/cos(x).  When x = pi/2+pi*eps/2, sin(x)
;; is essentially 1, but cos(x) is about pi/2*eps.  So tan(x) =
;; 1/cos(x).
(check-for-bug :alltest-legacy-1073
  (zerop (- (tan (/ pi 2)) (/ (cos (/ pi 2)))))	       
  t)

Perhaps that last test should not test for zerop but some relative
error between tan(pi/2) and 1/cos(pi/2)?

Ray


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